I was actually looking for a fish file (that damned bat starfish in a bowl) when I came across the base game files for butterflies and noticed they are actually kind of simple. Simple enough to do in a few hours, even.
This changes the appearance of:
Moth (it has feely antennae!!)
Monarch Butterfly
Zephyr Metalmark Butterfly
Red Admiral Butterfly
Mission Blue Butterfly
Green Swallowtail Butterfly
Royal Purple Butterfly
Silver-spotted Skipper Butterfly
Zebra Butterfly
Rainbow Butterfly (somewhat less ridiculous-looking!)
It doesn’t alter the butterfly meshes or flight patterns, it just makes them look less grainy and garbage-y.
No DLCs are required, just base game.
Download: SFS
TOU: please don't reupload these or link back to them with a paywall - my content is meant to be free for everyone. You can modify anything here for personal use however you'd like; if you feel like making your creations from mine available for the public, I'd appreciate it if you could please link back to this site.
Please note: Should Simfileshare become cranky with its links, replace the "simfileshare.net/download/" part with "simfil.es/" Leave the string of numbers be.